There are known devices which transfer a workpiece from one location to another within a machine. Such devices are used extensively in packaging machines. One such device, known as a rotary picking assembly, is shown and described in U.S. Pat. No. 5,215,515 to Breshadsky. That rotary picking assembly automatically opens and transfers carton blanks within a packaging machine. The assembly includes a plurality of picker arms that are moved along a closed circular path. Each of the picker arms includes a single suction cup in fluid communication with a vacuum pump. An additional supporting member is mounted immediately behind and moves together with the suction cups for preventing the carton blank from being tilted, misaligned, or knocked off during transfer.
In operation, a carton blank is initially gripped from a magazine or rack by the suction cup of the respective picker arm. The carton blank is broken open by a pivoted transverse member that swings from an open condition to a closed condition Ultimately, the open blank is transferred to a receiving member of a conveyor which transfers the carton to further portions of the packaging machine, for example, for filling and sealing.
Another rotary picking assembly is illustrated in U.S. Pat. No. 5,102,385 to Calvert. The assembly shown and described therein includes a suction cup device that moves radially inwardly and outwardly on a slidable rod as it orbits about a centrally rotating shaft.
In the rotary picking assemblies known in the art, the suction cups are directly supplied with a vacuum that is generated by a vacuum pump. Such vacuum pumps can be quite large and are often inefficient. Additionally, regulation of the vacuum supplied to the suction cups can be difficult to maintain in proper synchronism with the motion of the picker arms (i.e., activating the suction at selected portions of the transfer path). A more efficient and effective vacuum system is therefore desirable.